Heath incubator flow-through studies used a one 1 min-’ flow rate (Marking et al.,
1994). The one 1 min- ’ flow rate was selected during an extensive fungicide screening
project in which a low water flow rate was used because only limited amounts of test
chemical were available and an exposure duration of 60 min was typically used. Fish
hatcheries culture eggs in vertical flow incubator trays at an average flow rate of 18.9 1
min-’ (Brown and Gratzek, 1980). The flow of water required to incubate eggs varies
depending on the number of stacked trays, egg-loading rates per tray, and life stage of
eggs. However, hatchery personnel should be aware that a flow rate of 7.6 1 min-’ (2
gal min-I) or g rea t er is necessary to achieve expected treatment concentrations when
using Heath incubators.